For cultivation of cells, particularly eukaryotic cells, and more specifically mammalian cells, there is a constant need to use special culture media that make available the nutrient substances and growth nutrient substances that are required for efficient growth of the cells and for the production of the proteins or viruses that are desired. Cell culture media formulations have been supplemented with a range of additives, including undefined components like fetal calf serum (FCS), several animal-derived proteins and/or protein hydrolysates of bovine origin.
In general, serum or serum derived substances, such as albumin, transferrin or insulin, may contain unwanted agents that can contaminate the cultures and the biological products obtained therefrom. Furthermore, human serum derived additives have to be tested for all known viruses, including hepatitis and HIV, that can be transmitted by serum. Moreover, bovine serum and products derived therefrom, for example trypsin, bear the risk of BSE-contamination. In addition, all serum-derived products can be contaminated by unknown agents. In the case of serum or protein additives that are derived from human or other animal sources in cell culture, numerous problems (e.g., the varying quality and composition of different batches and the risk of contamination with mycoplasma, viruses or BSE agents) exist, particularly if the cells are used for production of medicinal agents or vaccines for human administration.
Therefore, many attempts have been made to provide efficient host systems and cultivation conditions that do not require serum or other animal protein compounds. Simple serum free medium typically includes basal medium, vitamins, amino acids, organic and inorganic salts, and perhaps additional components to make the medium nutritionally complex. Such media, however, often are nutritionally insufficient and must be supplemented with animal-derived protein supplements or recombinant versions of proteins used in cell culture, such as insulin, insulin-like growth factor or other growth factors.
To avoid the use of animal protein supplements in serum free cell culture medium, several attempts have been made to provide cell culture media that are completely free of proteins.
Cinatl et al., Cell Biology International 17:885-895 (1993) disclose the development of a media (PFK-1) specific for continuous propagation of VERO cells on a polyvinyl formal (PVF) culture surface.
WO 96/15231 discloses serum-free medium composed of a synthetic minimal essential medium and yeast extract for propagation of vertebrate cells and virus production process.
A medium formulation composed of a basal cell culture medium comprising a rice peptide and an extract of yeast or an enzymatic digest thereof, and/or a plant lipid for growth of animal cells is disclosed in WO 98/15614.
A medium comprising purified soy hydrolysate for the cultivation of recombinant cells is disclosed in WO 01/23527.
WO 00/03000 discloses a medium that comprises a soy hydrolysate and a yeast extract, but also requires the presence of recombinant forms of animal proteins, such as growth factors.
For efficient production of biological products, such as viruses or recombinant proteins, it is important that optimal cell density is reached to obtain maximal product yield.
Therefore, a current need exists to increase growth, metabolic activity and density of cells, and to provide optimal cell culture medium devoid of animal proteins for production of biological products, such as those used as medicinals or vaccines in humans. Furthermore, the down-stream processing, e.g. purification of the desired product from culture medium can be more cost-effective and time-efficient if animal proteins are not present in the medium. Additionally, unwanted immunogenic animal proteins may induce deleterious immunological reactions, which are avoided with practice of the present invention.